Roast flattened rice puffed rice, and amaranth separately and transfer to a bowl. Roast sesame seeds and flax seeds together and add them to the same bowl. To the roasted mixture, add some cashew nuts, peanuts, almonds, yellow and black raisins, chopped dates, chopped apricots, green and black grapes, and honey. Mix well by adding buttermilk and milk. Transfer bircher muesli to a serving bowl and serve.